In related arts, generally a metallic foil is used as a gas barrier layer in order to contribute to a barrier property against gas such as steam or the like.
In recent years, a gas barrier film including a deposited layer that is obtained by forming an inorganic oxide such as silicon oxide or aluminium oxide on a substrate film by the vacuum deposition method has been attracting attention. As the substrate film, For example, a biaxially-oriented polyester film that is excellent in translucency and rigidity is used.
In the above-mentioned gas barrier film, the deposited layer tends to be weak against friction and the like during usage. Therefore, when the gas barrier film is developed for various applications, a minute crack is generated in the deposited layer due to friction or stretching at the time of lamination, printing, filling of a content or the like, thereby possibly causing a gas barrier property to deteriorate.
Patent Documents 1 to 4 disclose a technique for laminating a coating layer on a deposited layer in order to protect the deposited layer.
Patent Document 1 discloses a gas barrier film in which a polyvinyl alcohol resin layer is laminated on a metal or a metal oxide that is formed on a surface of a substrate film (Claim 1).
Patent Document 2 discloses a gas barrier film that is framed by laminating, on a substrate film, a deposited layer consisting of an inorganic compound, which is referred to as a first layer, and a gas bather film that is formed through coating a coating agent containing a water-soluble polymer, alkoxide, hydrolysate thereof, or tin chloride, and drying by heating the gas barrier film, which is referred to as a second layer (claim 1).
Patent Document 3 discloses a coating composite for gas barrier that mainly consists of a particular organosilane and a particular silyl group-containing fluorine series polymer (Claim 1).
Patent Document 3 further discloses a was barrier film that is obtained by laminating, on a substrate film, a deposited layer consisting of a metal and/or an inorganic compound and a coating film formed of the above-mentioned coating composite (claim 11).
Patent Document 4 discloses a gas barrier coating composite containing a polyvinyl alcohol-based resin and a particular metal alcoholate (claim 1).
Patent Document 4 further discloses a gas barrier film obtained by laminating a coating film formed from the above-mentioned gas barrier coating composite on a substrate film (claim 10).
Further, Patent Document 5 discloses a method of manufacturing a gas barrier film that includes steps of (1) forming a film-like object of a composite that mainly consists of poly(meth)acrylic acid and a polyalcohol polymer, (2) applying a heat treatment on the film-like object, and (3) immersing the heat-treated film-like object in a medium containing metal (claim 15).
Patent Document 6 discloses a gas barrier film consisting of a polymer of unsaturated carboxylic compound multivalent metal salt containing a modified vinyl alcohol polymer (claim 1).